"Now...face the villain of your story"-Geralt

Geralt Fargus. Who is he? The mysterious man is seemingly behind everything....behind it all. Yet all we know about him is that he has a strange obsession with fate...and that he wanted to be a cook. Nevertheless , he's someone to be feared. His powerful magic almost decimated our heroes, and after the battle he didn't even seem fatigued...what is he working towards and why?